Controlling mechanism for automatic exchanges.



No. 875,951. PATENTED JAN. 7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES;

APPLIOATION FILED JULY 10. 1908.

11 SHEETS-SHEET 1.

No. 875,951. PATENTED JAN. 7,-1908. J. G. ROBERTS. CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

11 SHEETS-SHEET 2.

I jibc/v/a No. 875,951. PATBNTED JAN. 7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

11 SHEETS- SHEET 3.

No. 875,951. P ATENTED JAN. 7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

I 11 SHEETS-SHEET 4.

E i m? WEN #41 @i w E E No. 875,951. PATENTED JAN. 7, 1908.

J. G. ROBERTS. CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

ll SHEETSSHBET 5.

No. 875,951. PATENTED JAN. 7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

11 SHEETS-SHEET 6.

I ve;

No. 875,951. PATENTED JAN. 7, 1908.

J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

11 SHEETS-*SHEET 7.

WwKW

No. 875,951. PATENTED JAN. 7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLIUATION FILED JULY 10. 1906. I

l1 SHEETS-SHEET 8.

PATENTED JAN. 7, 1908.

J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION PILILD JULY 10. 1906.

11 SHEETS-SHEET 9.

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No. 875,951. PATENTED JAN. '7, 1908. J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLIOATION FILED JULY 10. 1906.

- 11 SHEETS-SHEET 10.

No. 875,951. PATENTED JAN. 7, 1908.

4 J. G. ROBERTS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

APPLICATION FILED JULY 10. 1906.

11 SHEETS-SHBBT 11.

15 F! ilj I UNITED STATES PATENT orunoE- JOHN G.- ROBERTS, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF

CHICAGO, ILLINOIS, ACORPORATION OF ILLINOIS.

CONTROLLING MECHANISM FOR AUTOMATIC EXCHANGES.

Specification of Letters Patent.

No. 876,951. I

Patented Jan. 7, 1908.

Application filed J ill? 10. 1906. Serial No- 326.454-

To all whom it may concern:

Be it known that I, JOHN G. ROBERTS, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Controllin Mechanism for Automatic Exchanges, of which the following is a specification.

My invention relates to switch'mechanism for controlling a system of circuits designed for use in an automatic telephone exchange wherein the operation of connecting two telephone lines for the purpose ofintercommunication is performed through the medium of mechanism operating automaticallyfwithout the intervention of an operator; and its rincipal object is to provide controlling mec anism that will produce the circuit changes required to bring about the operation of the automatic interconnecting devices with the highest possible degree of accuracy, efficiency and speed, while requiring the minimum of exertion in the manipulation of the controlling device mechanism. In the accomplishment of I so - and this object I have produced a circuit controlling device intended rimarily for use at the subscribers station 0 an automatic telephone line, and particularly adapted for employment in an automatic telephone exchange system such as that described herein, the novel features of which are claimed in my co-pending application Serial No. 305,272, filed March 10, 1906, of which the present a plication is a division. It will be understoo however, that the controlling device particularly described and claimed in this application is capable of use in systems other than that in connection with which it is-illustrated and described in the present instance, and thatan in which system the several stations on a 50 line may have their call signals or bells selectively actuated from the central ofiice. It is also designed to control the mechanisms at the central ofiice involved in establishing connection with other lines, and in transmitting the various signals incident to such interconnection, without recppiring the provision of the customary ear connection or common return conductor, or having recourse to the use of more than two conductors between the substation, or group of substations, and the central ofiice.

In the system in which I prefer to employ my invention I so organize the connectin and controlling mechanism at the centraoffice that its selective operation is effected by means of electrical impulses transmitted from the substations over a single circuit, the controlling or impulse transmitting mechanism at the substation being ada ted to impart to the currents sent over t e line certain peculiar characteristics to which the mechanlsm at the central office is selectively responsive. In this system the mech-' anism thus selectively operated b the impulses determined by the controlling mechanism serves, upon the initiation of a call at any one of the substations, to prevent any intrusion upon the calling line on the part of any other line by disconnecting the circuit through which connection is completed to the calling line, and at the same time establishing a peculiar electrical condition on the terminals of the line through which connection withit is completed, thus indicating that the line is engaged. It serves to find, in succession, trunks that are not in use extending throu h the groups of ten thousands, thousands, Iiundreds, and tens to the particular line with which the calling line is to be connected,- and, having selected the line, it serves to test its free or busy condition. If the selected line is enga ed, the mechanism responds to the pecuiar electrical condition existing upon its terminals, and transmits a tone or other distinctive signal to the calling subscriber to indicate that the called line is busy; if the line is not enga ed, 'the mechanism is actuated through t e agency of the controlling device at the calling substation to select the ringing current to which the station wanted is adapted to respond, and to apply this particular current to the line. It serves, after the ringing current has been applied to the called line a certain number of times without any response from the called substation,

4 automatically-to disconnect'the ringing current, and to ap ly a tone or a characteristic s' nal to the ca line to indicate that the ca ed subscriber oes not answer. If, on

Y the other hand, the subscriber responds to the calling signal, the mechanism operates automatically to disconnect the ringing current from the line, and to complete thecentral office mechanism through the medium of a single circuit extending between the substation and the central oflice, and havin no earth connection at the substation, so construct the circuit controllin device at the substation that it is adapter to modify the flow of current in the circuit, and produce a series of impulses, each impulse having a certain predetermined duration. The len th or duration of any of the impulses may Te varied by varying the relation to each other of parts of the controlling device provided for' that purpose; and the duration of each impulse determines the operation of a certain part of the automatic mechanism at the central oilice. The organization of this mechanism is such that each impulse of current in the circuit controls the movement of one of the switches concerned in the selecting of the called line and its interconnection with the calling line, and the extent ofmovement ,of each switch is dependent upon the duration of the particular current impulse to which it is adapted to respond. This result I attain by associating with each switch a constantly and uniformly moving part, which is brou ht into operative relation with the mova le member of the switch at the beginning of the current impulse, and which remains in operative relation with it until the im ulse ends, the switch member being held in t e position to which it has been advanced by suitable electrically controlled retaining mechanism.

In connection with the switches that are selectively responsive to the duration of the impulses, I provide other switches which, so to speak, distribute the impulses of the series each to its corresponding selecting switch, the distributing switch being selectively responsive to the numberof impulses, and not to their duration. I preferto arrange these distributing, or controlling, switches so that each will respond to certain consecutive impulses in the series, and not to the others, the switches having a step-by-step movement, one step for each of the imulses to which they are responsive, and bemg. retained in the position to which they are advanced in the last step by suitable electrically controlled mechanism. I am thus enabled, by providing a controlling device at the substation adapted to produce in the circuit of the line a certain number of impulses of current, each impulse having a certain predetermined duration variable at will, to eii'ect any desired selective actuation of the series of electrically operated switches at the central office which are involved in the selection of the called line, its interconnection with the calling line, and in the transmission to both the calling-and the called lines of the appropriate signals.

l viill describe my invention in connection.

nith the accompanying dranings, wherein Figures 1, 2, 3 and 4 taken together constitutc a diagranmiatic representation of the circuit which is involved in establishing connection between a calling and a called subs'cribers line in an automatic telephone exchange equipped for use ith my invention, and designed to accommodate up to one hundred thousand lines; Fig. 5, a front elevation, partially in section on line 5 -5 of Fig. 7, of the substation interrupter or circuit controlling device; Fig. 6, a seriional View of the same on lines 66 of Figs. 5 and 7; Fig 7 an end elevation of the interrupter partially broken away and in section on lines 77 of Figs. 5 and 6; Fig. 8, a front elevation of the outside of the interrupter '\\ith part of the inclosing shell broken away; Figs. 9, 10 and 11, detail views of parts of the interrupter; Fig. 12, a front elevation of one of the selecting switches arranged for actuation by magnetically controlled constantlymoving mechanism; Fig. 13 a side elevation of the same; Fig. 14, an elevation of one of the controlling or distributing switches:

pulses in the circuit of the line and the de termination of the duration or length of each impulse. .This mechanism I have designed with the particular object of meeting the requirements of the system vi-ith which in the present instance it is shown associated;

but it-will be understood that its form may be considerably varied-as, for instance, to

adapt it for use in association with other circuit arrangements without departing from the broad spirit of my invention. I

The substation interrupter, or controlling device, which \I find it convenient in the present instance to employ, is illustrated in Figs. 5 through 11, and is designated by the reference character G. It comprises. cssentially a switch g, or circuit controlling device, with mechanism for causing it to open and close its contacts a predetermined number of times, and to vary at will the length of time between interruptions. The switch and its controlling mechanism are supported on a frame consisting, ,in the svzspu present instance, of the base 9 from which project the partitions or flanges 9 and 9 over which an inclosing shell 9 is placed to inclose and protect the mechanism mounted within. The frame and shell may be metal, or of any suitable material. Theswitch 9 comprises a stationary part or anvil anda movable switch spring which normally rests upon the anvil, the spring having a projtecting portion which is adapted to be engaged b an adjusting screw g carried on the end of a bell crank lever g pivoted to the flange g of the frame on which the switch is mounted, the other end of the bell crank lever carrying a part 9 preferably in the form of a roller, which is adapted to be engaged by a disk g having a periphery provided with alternate elevations and deressions, so that as the disk is rotated the ever 9 is oscillated to alternately open and close the contacts of the switch g. The disk 9 is carried upon the end of an elongated ratchet wheel g j ournaled at its ends in the flanges g and g of the frame. The ratchet with its associated disk, whose alternate elevations and depressions correspond with the teeth of the ratchet, is turned step by step by a series of actuating .memb ers distributed along the length of the ratchet, and each adapted to cause the advance of the ratchet through one step. '1 hese actuating parts,.in

the present instance, are eleven in number, and are designated 9 g", g g, g, g i, g, g, g, 9 and 9 The general construction of the actuating parts is plainly shown in Fig. 11. Each part is, 1n the present instance, in the form of an armand with a shoulder 9 which is designed to engage a sto bar 9 extending transversely across the rame, .to limit the downward movement of the actuating part and prevent it from' advaiicin the ratchet wheel more than one step. hach arm also carries aratchet portion, preferably extending upward from the arm on the arc of a circle concentric with the shaft or sleeve upon which the arm is journaled, and havin asmany teeth as may be required. In t e present instance, g, g, g and g are each provided wit ten ,teethas shov n in Fig. 11, g

with four teeth, g", g and g each with but one tooth, while g, the last memb er in the series, has no teeth. Each arm also bears a pawl 9 preferably on the side of the arm away from the ratchet, adapted-to engage and cooperate with the teeth of the ratchet carried on the adjoining arm.

Between certain of the actuating arms shielding members of the character illustrated in Fig. 10 are interposed. Each of these members comprises an arm fulcrumed at one end of the sleeve 9, upon which the actuating members are fulcrumed, and provided at the other endwith a portion 9 adapted to be interposed between the pawl of one actuating memberand the ratchet portion of the next actuating-member in the series. This shielding portion 9 may con veniently be formed, as shown, by bending the-arm laterally at right angles to its plane, the forward ortion of the arm being again bent forward y into a plane parallel with that of the rear portion of the arm and carrying a segmental enlargement g, provided with a knurled edge adapted to roject through a corresponding slot in the p ate 9 in the front of the interrupter. Pro'ecting laterally from the segment 9 of the s ielding member is a portion 9 on an are having its center in the axis of the sleeve on which the member is journaled, and provided on its lower portion with numerals or suitable characters brought into view one at a time through a corres onding aperture in the front plate 9" to lIl( icate the extent of displacement of the arm about its shaft, and on the upper portion with corrugations corresponding in number and separation with the number and separation of the characters on the lower part of the lateral projection, and designed to cooperate with a retaining finger g to hold the shielding arm in any posltion to which it may be moved by means of its projecting knurled edge. Each shielding arm is also provided with a part ada ted to engage the stop bar 9 to limit the ownward movement of the arm. Mounted upon the shaft or sleeve 9 adjacent to each of the actuatin arms, and secured to the sleeve so as not to e rotatable thereon, is a collar 9 which serves as an abutment for a spiral s ring 9 the other end of which is secured to t e actuating arm, and which serves to return the arm to its normal resting osition against the stop bar 9 after it has con displaced therefrom. No retracting springs are provided'for the shielding members, which are adapted toreniain in the position to which they are manually moved.

In the arrangement as described the operation of the switch g is effected by the return of the actuating members to their normal resting ositions, one after the other, after having been displaced therefrom. To provide for their displacement, and their return to normal position at a uniform and invariable rate of speed, I provide the following mechanism: Through the hollow shaft or sleeve 9 there extends a shaft g, which ter- &

minates at one end in a'screw-threaded portion upon which is a nut g extending over the end of the sleeve g to prevent the longitudinal displacement of the shaft in the sleeve, and at the other end is provided with an enlarged portion or head pinned to an extension shaft g, which is journaled in the flange g of the frame, and to the end of which a handle 9 is secured. The hub of the first actuating arm, 9, of the series is rigidly secured'to the enlarged portion of the shaft to rotate therewith, While the hubs 0f the other actuating and shielding arms are, as has heretofore been stated, loosely mounted on the sleeve g so as to be capable of rotation thereon. The sleeve 9 is supported at one end by a screw-threadediportion of reduced diameter which passes through the flange 9 and is secured thereto by means of a nut, as shown, and at the other end by its engagement with the enlarged end of the shaft 9 which is rotatable within it.. To

rovide for the restoration of the shaft and 1ts associated parts after they have been turned from their normal position by means of the handle g, I employ, inthe present instance, a spiral spring g one end of which is suitably secured to the enlarged end of the extension shaft 9 while the other end is made fast to an abutment 9 mounted upon the frame; and in order that the restoration of the shaft-from its displaced to its normal position may be at a uniform and invariable rate of speed, I employ a heavy balance wheel g and escapement mechanism comprising an escapement g suitably fulcrumed, and connected with the balance wheel by means of a spring g secured to an abutment g on, the wheel, together with an escapement wheel g journaled upon the extension shaft 9 By means of a ratchet wheel, 9 rigidly secured to the escapement wheel and adapted to be engaged by a pawl g carried on an arm 9 rigidly secured to the extension shaftg I bring about the result that the movement of the shaft 9 is under the control of the escapement mechanism only in the return movementof the shaft, the pawl on arm 9 acting to couple the arm With the esca ement wheel only in the return movement 0 the arm. The balance wheel is made of such relatively large mass, and the spring'which connects it with the escapement is so proportioned that the movement of the escapement wheel, and the shaft which it controls, is slow and at a practically uniform rate of speed. The balance wheel, as shown,

is journaled between a bridging support 9 and the flange g of the frame.

As has been stated, the hub of the actuat ing arm 9 the first in the series, is rigidly secured to the shaft g and it is through this arm that movement is lmpartd to the other arms inthe series in the operation of the device. Whenthe handle g is turned to cause the rotation of the shaft, the arm g is caused to rotate, and the pawl g carried at the end of the arm is brought into engagement with one of the teeth of the ratchet portion of the next actuating arm in the series, the tooth en-v gaged depending on to what extent the shield of the intervening shielding member of arm 9 is interposed between the pawl and the to' which any one of the actuating members 1 will be moved before movement is imparted to the next member or arm in the series will depend entirely upon the extent of interposition of the shield of the intervening shielding member between the pawl of one and the ratchet of the other; and that therefore the interval of time which will elapse between the return to its normal position of one actuating member and the return to its normal position of the preceding actuating member of the series in the'return movement of the mechanism, and hence the interval between actuations of the switch 9, may bepredetermined by moving the intervening shielding member through any predetermined arc It will be noted that certain of the actuating members, namely, 9, g, g and g, a

trols does not require at these pointsin the sequence of impulses an impulse of variable duration, and therefore it is suflicient' to provide for a current impulse of any certain fixed duration by employing but one tooth, and locating it so as to insure a fixed and constant movement of the preceding member before movement is imparted to this member. The function of the shields at the points in the series where they. are located is, so to speak, merely toprovide means for efi'acing or rendering inoperative all of the teeth but the first one with which engagement is permitted, and, by being made movable in their relation to the teeth of the associated ratchet, to make the position of the operative tooth variable at will.

When, in the use of the interrupter described above, a call is to be made for a particular line' in the exchange, the position of tures in the face plate, reading from left to right, to correspond with the number of the station with which connection is desired. When this is done, eachshield is so interposed between its associated members as to produce certain time intervals between the starting of their respective movements when the handle is turned to set the device, and between the ending of their movements when normal positions. Actuating member 9 is the first to be moved from its resting position, .and member 9 the last; and in the return movement 9 is the first to return to its 5 home position and g the last, each member in succession as it returns to its home position turning the ratchet 9" one step, and through the medium of the disk g and the lever g, causing the switch 9 to open and close 1ts circuit. This succession of makes a and breaks in the circuit which the switch 9 controls following each other at predeter-..

mined intervals, varying according to the op I erative relation of the actuating members to each other, effects the selective actuation of the central office mechanism in a manner hereinafter to be described. The shields, it will be observed, remain in the positions in which they are set, thus enabling 'the call to be repeated Without the necessity of again setting up the number; while the actuating members are moved back to their normal positions each by means of its associated spring g which has been put under tension in the setting movement of the handle," the return .movement of the shaft merely servin through the medium of the interconnects .slil'ies of'members to retard their return movement and regulate the same to a con- 40 stant and uniform speed.

I will now describe the switch which Ihave designed to respond selectively to the .duration of the current impulses determined by the substation interrupting mechanism, such as that just described. One form of switch which I find it convenient to employ, is illustrated in Figs. 12 and 13. So far as. the switch mechanism roper is concerned it does notdifier great y from that employed in a well known automatic telephone exchange s stem, and which is illustrated and describe -in-Patent No. 638,249, issusd De *c'ember 5, 1899 to Keith & Erickson; the principal feature of difierence bein in the organization which I have provide for effecting and controlling the movement ofthe movable switch members. The switch comprises, in the present instance, a frame consisting of two parallel rods k? and transverse plates k" upon which-are mounted the movable and stationary switch contact members and the mechanism for operating them. The movable ,members'k, and a g b secured to a rodk', from which they are nsu 6 'lated byv insulating-sleeves k Associated the members are allowed to return to their.

step-by-ste bers are adapted to be brought into contact 'with any one of the fixed or stationary contact members by two movements, one vertical, and the other horizontal, the vertical movement being first caused to bring the movable member opposite a particular row of contacts with pne of which the connection is to be made, and the rotary movement causing the arm to sweep over the contacts in that row until it completes connection with the one desired. It has been customary to effect this movement of the movable members of the switch by: means of two electro magnets operating t rough ,the medium of mechanism, one to raise the shaft or ro 7c step by step the desired distance, and the otherto rotate it step by step until the desired fined contact is engaged. In accordance with my invention I employ, instead of this step-by-step mechanism, constantly moving. parts magnetically moved into en agement with a part associated with the rod to efiect the vertical movement and the horizontal movement of the rod. The. driven part, or part associated with the rod, is shown in t e present. instance as cylinder is whiclr'is adapted to be enga ed by two constantly rotatlng disks k and the first. mentioned disk being adapted, when it is moved into contact wlth the driven cylinder k to cause the shaft or rod k with its associated switch members to move up, while the disk k when moved into contact with the driven cylinder, is adapted to impart to the rodand its associated switch arms a movement ofrotation. Thedisks k and k are similarl' arranged, both being fulcrumed in the en of levers k, 7:, respectively, and both bein in enga ement wlth constantly rotating isks'k fit", respectively, carried upon shafts k, k, respectively, which are constantly and uniformly driven by any suitable source of power. The levers 7c", in, re

spectively, are fulcrumed upon, or concentric with, their associated shafts k and k,

ium of its armature a switch 7& with which a roller kl, or like part carriedu on the end of the armature, is adapted to e*brought into engagement when the magnet is energized. In order to effect the appropriate movement of the movable switch members, the mechanism actuated by the magnetic is mounted sothat disk rotates in a vertical plane just out of contact with the driven Ir, a horizontal retaining ratchet k, and a' magnet k", the armaturek of which cooper:- ates with two pawls 7c and 7c, the first of which is adapted to engage the teeth of'the horizontal retaining ratchet k,- and the lat ter theteeth of the vertical retainin ratchet is when the magnet is energized. pon the deenergization of the magnet the armature operates upon the pawls k and 1c to cause them to release their associated ratchets,

whereupon the shaft is with its movable switchmembers is free to return to its normal position. The vertical retainingratchet 7c is made in the form of a cylinder around the circumference of which the teeth extend, so that the pawl which engages the teeth does not .prevent the rotation of the shaftk after it has been raised the required distance; and likewise the horizontal retaining ratchet 7c is in the form of a cylinder with the teeth extending longitudinally thereof, to ermit the vertical movement of the shaft while pre-' venting its horizontal rotary movement.

In the operation of the switch, an impulse of current 1s caused to pass through magnet 70 which responds by attracting its armature and bringingdisk 7c into contact with As the disk is conthe drivencylinder 79 stantly-rotated, it immediately causes an 11 Ward movement of the cylinder, and, as tl e s eed of rotation is maintained uniform at a times, the extent of the upwardmove ment is exactly determined by the length of time during which the impulse of current passes through the magnet.

upon causes an impulse of current to traverse the coils of magnet k which, responding,

moves the constantly rotating disk k into.

contact with the driven cylinder and thus 1mparts to the shaft 70 and its associated The driving When the current ceases the constantly rotating disk 7c is immediately withdrawn from the cylinder,-

Theoperation of the controlling mechanism there' switch members a movement of rotation. This movement takes lace at a uniform rate, and ceases immediately upon the cessation of the current flow in the magnet 7c,

the extent of movement thus dependingup pln e the duration of the current impulse.

shaft is held in the position to which it has.

been rotated by the engagement offpawl it from atthe outset of the movement of rotation of the arm.

In Figs. 14, 15 and 16 isillustrated another form of switch which -I find.it con venient to employ. This switch does not.

differ greatly from types well known in the art, anddoes not require extended description. It comprises a frame it" arranged to be secured to any suitable support, and upon 1 which the arts of the device are mounted. The movab e contact members of the switch -12 k h and h are mounted upon, but insulated'from, a rod or shaft h fulcruined in the support, and provided with av spri k for returning it to its normal position w en it is moved therefrom.- Each movable switch member 006 erateswith a series ofstationary or .fixe contact terminals h being adapted to com lete connectionwith one after the other 0 the contacts as it'is'swung about the rotation of the rod. Movement is imparted to the rod and the associated switch members by means of an electro-.

magnet hf throughthe medium of a pawl it carried upon thearmature h of the magnet,

and cooperating with a ratchet 72, mounted,

in the present instance, upon the upper part of the rod. The switch arms are maintained in the position to which they have been moved b means of'a'retaining pawl h normally he (1 away-from the ratchet h b the engagement therewith of the armature of another magnet h,..the retaining awl being\ allowed to come in contact with t e ratchet when the magnet Wis energized to attract its armature. To render the-mechanism. incapable of advancing the movable switch members beyond the last stationary terminal each is adapted to engage, and hence irres onsive to all .buta redetermined number 0- the current im u sesthat traverse the ma net It, I provide the ratchet wheel 7 Wit ly as-many teeth each for'the ad vancing pawl and the retaining pawl as correspond withthe advanced positions which the movable members are adapted to occupy. Any further actuation of the magnet h is thus ineffective to cause a further advance of the switch arms. The magnet 72, is also arranged'to operate a switch h the members of which are suitably mounted upon but insulated from the frame, the arrangement being such that the switch maintains its contacts open so long as the armature is retract-.

ed, an closes them when the magnet isenergized. The switch shown associated with the magnet h,'in the present instance, comprises only two contact members; but any other number and combination ofcontact members ma be substituted as the circuit or circuits to be controlled require. Likewise, although the resent switch is illustrated as bei provi ed with four movable contact mem ers each adapted to cooperate with four fixed or stationary contact terminals, it will be understood that any other combination of movable and'fixed members may be provided as desired. v

I shall now describe the circuits b .means of which the mechanism describe in the foregoing, together with other ap aratus which is well known and requires no etailed description, is combined in an organization which the circuit changing device of my invention is adapted to control. The circuit organization is illustrated diagrammaticall in Figs. 1, 2, 3, and 4 of the drawings, whic illustrate two telephone lines, each rovided with a plurality of substations, to et er with the series of circuits which would e required to link them together for conversation assuming that the were in an automatic telephone exchange a apted to serve up to one hundred thousand lines. The various controlling and interconnecting switches are diagrammatically indicated, and will be recognized as being similar to or of the type of the switches described in the foregoing portion of the s 'ecification. For the sake of simplicity in i ustration, many parts of the mechanism which are not essential to the understanding of the circuit connections are omitted, includin all excepting part of one horizontal row 0 stationary contacts in each bank of the switches adapted for both vertical and horizontal movement; and for the same reason a number of batteries and earth connections are shown at different points in the fig-' ure's, whereas it will be understood that these batteries mi ht be, andin most cases would be, one and t e same battery ada ted to supply current for the operation of the entire system, while the connections illustrated as being to earth might be to a single common return conductor.

The scheme for effecting interconnection between any two lines in the exchange which is followed in the resent instance ma briefiy'stated as fo owszEach subsc'ri ers line is terminated upon the movable memwhich are adapted in another position to connect the line with stationary contact terminals of other switches throu h which connection is completed with the ine in case of a call incoming to 'it. The movable contact terminals of the cooperating switch associated with each line are adapted to complete connection with' any trunk which is not usy ofa number terminating upon the stationary or fixed terminals of the switch. This trunk extends to the movable terminals of another automatic switch which may have ten rows of fixed terminals, representing the ten roups of ten thousand lines each into whic the exchange may be divided, and as many contacts in each row as there are trunk of the larger roup are divided, while the contacts in eac row represent the number of trunks extendin from this switch to the particular thousan lines represented by the row. The predetermined vertical movement of the movable members of this switch selects the particular thousand group desired, and the horizontal movement finds a trunk which is not busy and completes connection with it. found terminates upon the movable members of a switch whose ten rows of fixed The-other end of the trunk i contacts represent ten groups of a hundred each into which the group of one thousand lines is divided, and whose contacts in each row represent the trunks extending to this particular hundred. In like manner, the vertical movement of the movable members of the switch selects the particular hundred desired, while the horizontal movement finds a free trunk extending to this hundred and makes connection therewith. The other end'of the trunk thus selected extends to the movable members of the switch which serves to complete connection with the particular line called, the ten rows of contacts representin the ten groups of ten mto which the hundre is divided, and the ten contacts in each row bein connected with the ten individual lines w 'ch that row re resents. The vertical movement of the r'nova le-mern ber selects the proper tens group, and the the calling line A A A and A, and the four substations of the called line, A A, A

and A. Each substation is provided with the usual telephonic apparatus, comprising in the present instance the call bell a, a condenser a, an induction coil a a transmitter a a telephone receiver a and a switch hook a and in addition there is provided at each substation an interrupter or circuit controller G of the type hereinbefore described, or of any form which will perform the work of this interrupter. The telephone line extends from the four substations A A A and A in two limbs 1 and 2 to the movable terminals of a controlling switch H at the central ofiice B, while the telephone line which serves substations A A, A and A extends in two limbs 23 and 24 to the movable terminals of controlling switch H at the central office desi ated F. An extension of the telephone line 1, 2 connects with the fixed or stationary contact terminals vof a number of connecting switches U subect, however, to the control of switch H, while the limbs 23, 24 of the other telephone line extend to the fixed contact terminals of a number of connectin switches U subject to the control of switc H Each line en-' tering the exchange has, in the present instance, a normal connection with the poles of a central battery V, one of the limbs of theline including the magnet which serves to actuate the controllin switch onthe movable members of whic the line terminates. To avoid confusion, this arrangement isnot illustrated in the case of the line extending from the substations A A", A

and A to the central oflice; but in' the case of the line extending from substations A A A and A the magnet h is shown included between limb 2 of the line and the free pole the battery V. To provide a return path for the current which flows to the line through magnet h, and at the same time to balance the line against inductive disturbances, an inductance or retardation coil b is connected between the limb 1 of the'line and the other or grounded pole of the battery.

. mounted on butinsulated from the shaft h the, rotation of which -is "controlled by the magnet h"; and, as shown, each armisadapted normally to rest on one and to be broughtintocontact with threeJother stationary contact terminals. The :first two stationary. contacts of each series engaged. by contac't' arms h and k of the switch are connected with conductors 25 and26 extending to the stationary contact terminals which represent the line terminating on switch H on the va-.'

rious connecting'switches U In their third position the arms h h rest on dead or disconnected terminals and in their fourth position extend the circuit of the conductors 1 and 2 of the line to conductors 3 and 4 which are connected with contact arms 7' and i of the associated finder switch I. The arm 7?, which is connected to earth, or the earthed ole of the battery, completes no circuit in lts normal or resting position, but in its second, third and fourth positions grounds conductor .27, which is connected -on switches U to the stationary terminals associated with conductors 25 and 26, and which serves as a test conductor to indicate, by its changed electrical condition when the switch H is operated, that'the line 1, 2 is en aged. The arm h of the switch is connecte with the free pole of the central battery V and completes no circuit either in its first, or normal, or in its second position; but in its third and fourth positions closes a conductor 28 which extends throu h the actuating magnet i of the associate finder switch I, and thence to earth or the other pole of the battery by way of the resting contact of arm 'i of that switch, and which also has a branch 29 extending to earth through the winding of the retaining magnet i of the switch I.

The windingof retaining ma et h is included in a conductor 33 exten ing between the poles of the battery, and controlled by contacts h of the actuating magnet h of the switch, the circuit being closed to energize the retaining magnet to allow the pawl h to engage the ratchet it, when current flows through the winding of the magnet h. t It is necessary that the pawl h shall be in engagement with the ratchet to retain the switch in its advanced position while the armature k 'ofthe magnet h is being moved back and forth by the impulses in the line circuit to advance the switch; andin order that the pawl ma not be released during the brief intervals when the armature h is unattracted, and conductor 33 therefore opened- "at contact h, I preferably make the ma et h? sluggish in its action by shunting its winding wit a resistance h" which serves'to' take the discharge of the magnet and cause current to continuecirculate in the local-circuit during the {momentaryinteri'uption of conductor 33.jfAny interruption of the circuit lon er thanthe momentary one which occurs as t e armature of magnet h moves back and forth in causing the step-b -step advance of the switch arms, permits t e denergization of magnet h thus makingitheretaining' pawl inoperative and permitting the switch to re- "turnto its normal position. It will be un-.-,

derstood that this result may be obtained,

and {the relativel sluggish operation of re--' taining pawl' hfi eefiected'in a number of other ways well-known in the art.

Referring now more particularly. to the finder switchI, which is associated with con-' the same as the switch illustrated in Figs. 12

and 13 of the drawings and hereinbefore described; excepting that it has but a single row of stationary contacts for each movable switch arm, and therefore is enabled to dispensewith the mechanism for efiecting a verticalmovement of the switch arms. This switch has four arms 1', i i and t the first two and the last of which, as has been previously stated, are connected to conductors 3 and 4 and to earth, respectively, while arm i is normally connected by way of conductor 30 to earth through the resting contacts of the switch 11 operated by the actuating magnet .of the switch I, and, in the alternative position of the switch, to the portion of conductor 28 extending between the actuating magnet i and the restin contact of arm i. The fixed terminals, with which arms i, t and i are adapted to come into engagement as they are rotated, are connected with the conductors of a number of trunk lines, the two line conductors 5, 6 of each trunk being terminated upon corresponding contacts of the series with which arms i and i cooperate while the local or test conductor 31 associated with each trunk is terminated upon a corresponding contact of the series which arm '5 is adapted to engage. In the drawing but a single trunk 5, 6 is illustrated, with its conductors'5, 6 and 31 connected to other like finder switches I, but it will be understood that the other stationary contacts, of

which there may be any desired number, of

v the switch I are all likewise connected to one of the four substations connected wit Other trunks.

In the operation of the controllin switch H and the finder switch I describe above, the closure of the telephone switch at an line 1, 2 closes a circuit whereby current may 'flowsteadily out throu h actuatin magnet h of switch H and bac through t e retardation coil 1;. This causes the actuating magnet to attract its armature and advance all of the arms of switch H one step, from their first or normal to their second position,

which, it will be seen, does not interrupt the circuit normally existing between line 1, 2 and conductors 25, 26 extendin to the connecting switches U but merey serves to cause arm h te connect conductor 27 to earth to make line 1, 2 busyigato other lines. The first of the succession'oi current impulses determined in the line by the operation of interrupter G at the substation advances all of the arms of switch H to their third position and thereby disconnects con- .duotors 25, 26 from the line, but does not affeet the connection which has been established between conductor 27 and earth. The first impulse of the series also, in advanc ing arm 'h to its third position, closes the circuit of conductor 28 and thereby brings about the energization of magnet i of the finder switch I to allow the retaining pawl tov The shaft i of switch I thereupon starts to rotate, causing the contact arms to swee over the fixed contact members upon which the various trunks 5, 6 terminate. In the first stage of the movement of the switch arms, arm '8 breaks the earth connection of conductor 28 in which the winding of actuating magnet t is included; but the actuating magnet, in moving the rotating disk 11? into contact with the driven disk to cause the rotation of the switch, also operates switch i causing the switch spring to open its normal and close its alternative contact, which completes a circuit for actuating 'magnet '1', through conductor 30 to the arm '5 of the switch. This arm in the movement of the switch is swe t over the contacts upon which the loca or test conductors 31 of the various trunks terminate, and as, as will hereinafter be described, these conductors are grounded when the trunks with which they are associated arebusy, the actuating circuit for magnet i will be completed and the rotation of the switch arms will continue so long as the arm i is moving over terminals representing trunks that are busy. But as soon as it passes onto the contact of a trunk which is free,-it finds no circuit for the current flowing through actuating magnet i", and that ma net is denergized and permits the constant y rotating disk i to be disen- 1gaged from the driven disk, the switch arms emg maintained in the position to which they have been moved by retaining pawl 41. As soon as the actuating magnet 1s dener- 'gized, the spring of switch 6, returns to its normal resting contact and thereby applies a ground to conductor 30, thus ounding the test contacts of the trunk with which connection has been made at all the switches to which the trunk is multiplied, and prevent ing the trunk from being appropriated by any other switch. The second impulse of current determined by the substation interrupter now occurs, and advances all of the arms of switch H to their fourth and last position, causingarms h rand h to extend the circuit of line 1', 2 to conductors 3, 4, which have just been connected to trunk conductors 5, 6 by switch I The advance of arms 71 and h to their fourth position does not effect any change in the circuits which the a control, the conductor 27 remainin groun ed to keep the busy test con ition on the associated terminals of the switches U and the circuit of conductor 28 remaining grounded to maintainenergized the retain- 

